Polydeuces (also known as Pollux) was the twin brother of Castor. Both Castor and Polydeuces had the same mother, Leda, but Polydeuces' father was Zeus, while Castor's father was a mortal man named Tyndareus; because of this, Castor was mortal while Polydeuces was immortal. When Castor died, Polydeuces asked Zeus to let him share his own immortality with his twin to keep them together and they were transformed into the [//en.wikipedia.org/wiki/ Gemini constellation].